Motor unit

ABSTRACT

A motor assembly includes a motor, a controller on one side in an axial direction of the motor, and a motor cover between the motor and the controller in the axial direction. The controller includes a screw. The screw includes a head portion located on one side in the axial direction of the motor cover and a screw portion extending from the head portion to the one side in the axial direction. The motor cover opposes the head portion in the axial direction. A length of the screw in the axial direction is longer than a distance between the controller and the motor cover in the axial direction. The motor includes a pin extending to the one side in the axial direction. The motor cover includes a hole portion into which the pin is inserted. The screw is at a position shifted from the hole portion as viewed in the axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2021-214279, filed on Dec. 28, 2021, the entirecontents of which are hereby incorporated herein by reference.

1. Field of the Invention

The present invention relates to a motor assembly.

2. Background

A conventional motor assembly includes a motor and a control board thatcontrols the motor. The control board is fixed with screws.

When a screw to fix the control board is loosened and falls off, thefixation of the control board becomes insufficient, and the vibrationgenerated in the control board increases.

SUMMARY

A motor assembly according to an example embodiment of the presentinvention includes a motor including a rotor rotatable about a centralaxis and a stator radially opposing the rotor, a controller on one sidein an axial direction of the motor to control the motor, and a motorcover between the motor and the controller in the axial direction andcovering the motor from the one side in the axial direction. Thecontroller includes a screw. The screw includes a head portion locatedon the one side in the axial direction of the motor cover, and a screwportion extending from the head portion to the one side in the axialdirection. The motor cover opposes the head portion in the axialdirection. An axial length of the screw is longer than a distancebetween the controller and the motor cover in the axial direction. Themotor includes a pin extending to one side in the axial direction. Themotor cover includes a hole portion into which the pin is inserted. Thescrew is at a position shifted from the hole portion when viewed fromthe axial direction.

The above and other elements, features, steps, characteristics andadvantages of the present disclosure will become more apparent from thefollowing detailed description of the example embodiments with referenceto the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a motor assembly according to an exampleembodiment of the present disclosure.

FIG. 2 is an exploded perspective view of a motor assembly according toan example embodiment of the present disclosure.

FIG. 3 is a longitudinal cross-sectional perspective view of a motorassembly according to an example embodiment of the present disclosure.

FIG. 4 is a perspective view of a control board according to an exampleembodiment of the present disclosure as viewed from below.

FIG. 5 is a perspective view of a motor cover according to an exampleembodiment of the present disclosure as viewed from above.

FIG. 6 is a perspective view of a motor cover according to an exampleembodiment of the present disclosure with a reverse surface facingupward.

FIG. 7 is a plan view of a motor cover according to an exampleembodiment of the present disclosure as viewed from above.

FIG. 8 is a view schematically illustrating a protruding portion of amotor cover and its periphery according to an example embodiment of thepresent disclosure.

FIG. 9 is a view schematically illustrating the positional relationshipbetween a screw inserted into the control board and the motor coveraccording to an example embodiment of the present disclosure.

FIG. 10 is a view illustrating a state in which a screw illustrated inFIG. 9 has moved downward.

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present invention will bedescribed with reference to the accompanying drawings.

In the present specification, a direction in which a central axis CA ofa motor 1 extends is referred to as an “axial direction”, and one sideand the other side in the axial direction are respectively defined as anupper side and a lower side. However, the definitions of upper and lowersides do not limit the orientation and positional relationship when amotor assembly 100 is used.

In addition, in the present specification, a radial direction centeredon the central axis CA is simply referred to as a “radial direction”, adirection approaching the central axis CA in the radial direction issimply referred to as a “radially inside”, and a direction away from thecentral axis CA is simply referred to as a “radially outside”. Acircumferential direction centered on the central axis CA is simplyreferred to as a “circumferential direction”.

FIG. 1 is a perspective view of the motor assembly 100 according to anexample embodiment. FIG. 2 is an exploded perspective view of the motorassembly 100 according to the example embodiment. FIG. 3 is alongitudinal cross-sectional perspective view of the motor assembly 100according to the example embodiment. FIG. 4 is a perspective view of acontrol board 21 according to the example embodiment as viewed frombelow.

The motor assembly 100 according to the present example embodimentincludes the motor 1, a controller 2, and a motor cover 3. The motorassembly 100 includes a housing 4. The motor 1, the controller 2, andthe motor cover 3 are housed in the housing 4.

The motor 1 includes a rotor 11 and a stator 12. The rotor 11 isrotatable about the central axis CA. The stator 12 radially faces therotor 11. The motor 1 includes a bus bar unit 13.

The rotor 11 has a shaft 10. The shaft 10 extends in the axial directionalong the central axis CA. The shaft 10 is rotatably supported by alower bearing 101 and an upper bearing 102. The lower bearing 101supports the lower side of the shaft 10, and the upper bearing 102supports the upper side of the shaft 10. The shaft 10 forms the rotationshaft of the motor 1.

The rotor 11 includes a rotor core 111 and a rotor magnet 112. The rotorcore 111 has a cylindrical shape extending in the axial direction. Therotor core 111 is formed by stacking a plurality of electromagneticsteel plates in the axial direction. The shaft 10 is press-fitted intothe rotor core 111. As a result, the rotor core 111 is rotatabletogether with the shaft 10. A plurality of rotor magnets 112 are fixedto the radially outer surface of the rotor core 111. The plurality ofrotor magnets 112 are arranged along the circumferential direction.

The stator 12 is disposed radially outside the rotor 11 and rotates therotor 11. The stator 12 includes a stator core 121, an insulator 122,and a coil 123. The stator core 121 has an annular shape centered on thecentral axis CA. The stator core 121 is formed by stacking a pluralityof electromagnetic steel plates in the axial direction. The rotor 11 isdisposed radially inside the stator core 121.

The insulator 122 covers at least a part of the stator core 121. Theinsulator 122 is an insulating member using resin or the like. The coil123 is formed by winding a conductive wire around the stator core 121through the insulator 122. The coil 123 is connected to the bus bar unit13. The bus bar unit 13 supplies drive power to the coil 123.

The bus bar unit 13 is disposed above the stator 12. The bus bar unit 13includes a bus bar holder 131. The bus bar holder 131 holds a bus bar(not illustrated) of each of the U, V, and W phases. The bus bar of eachphase is connected to the coil 123 of a corresponding one of the phases.The bus bar of each phase is connected to the controller 2.

The bus bar unit 13 has a pin 130 extending upward. The pin 130 extendsupward from the upper surface of the bus bar holder 131. The bus barunit 13 is a constituent element of the motor 1. That is, the motor 1has the pin 130 extending upward (to one side in the axial direction).

For example, the bus bar held by the bus bar holder 131 has an arc shapewhen viewed from the axial direction. The bus bar holder 131 has anannular portion centered on the central axis CA in order to hold thearc-shaped bus bar. The pin 130 is disposed in the annular portion ofthe bus bar holder 131. The number of installed pins 130 is plural. Theplurality of pins 130 are arranged in the circumferential direction.

The pin 130 has, for example, a columnar shape extending in the axialdirection. However, the shape of the pin 130 is not particularlylimited. The number of installed pins 130 is also not particularlylimited. The pin 130 may be the same member as the bus bar holder 131,or may be retrofitted to the bus bar holder 131.

The controller 2 controls the motor 1. For example, the controller 2controls power supply to the motor 1. The controller 2 is on the upperside (one side in the axial direction) of the motor 1. The controller 2includes a control board 21 disposed above the motor 1. The controlboard 21 expands in the radial direction.

For example, a sensor magnet 110 is disposed at the upper end portion ofthe shaft 10. The sensor magnet 110 is a permanent magnet and has an Npole and an S pole. The sensor magnet 110 rotates together with theshaft 10. That is, the sensor magnet 110 rotates together with the rotor11.

A sensor (not illustrated) is on the lower surface of the control board21. The sensor detects the rotational position of the rotor 11 based onthe magnetic flux of the sensor magnet 110. Power supply to the coil 123is controlled based on the rotational position of the rotor 11.

The motor cover 3 is between the motor 1 and the controller 2 in theaxial direction and covers the motor 1 from the upper side (one side inthe axial direction). More specifically, the motor cover 3 is disposedto face the lower surface of the control board 21 at an interval in theaxial direction. The motor cover 3 is fixed to an upper end portion ofthe bus bar unit 13. That is, the motor cover 3 covers the bus bar unit13 from above. By disposing the motor cover 3 between the motor 1 andthe controller 2 in the axial direction, it is possible to suppress theadhesion of foreign matters such as dust to the bus bar unit 13. As aresult, it is possible to suppress the mixing of foreign matters intothe motor 1. The shape of the motor cover 3 will be described in detaillater.

The housing 4 includes a motor housing 41, a bearing holder 42, and anupper cover 43.

The motor housing 41 has a bottomed tubular shape. That is, the motorhousing 41 has a bottom portion extending in the radial direction. Thebottom portion of the motor housing 41 has a through-hole penetratingthe axial central portion in the axial direction. The rotor 11 and thestator 12 are disposed radially inside the motor housing 41. The lowerend portion of the shaft 10 protrudes downward from the bottom portionof the motor housing 41, and the upper end portion of the shaft 10protrudes upward from the upper opening of the motor housing 41.

The motor housing 41 has a lower bearing holding portion 411 at thecentral portion in the radial direction. The lower bearing holdingportion 411 is a portion recessed downward from the bottom surface ofthe motor housing 41. The lower bearing holding portion 411 holds thelower bearing 101. More specifically, the lower bearing 101 is disposedinside the recess constituting the lower bearing holding portion 411.

The motor housing 41 has a tubular portion. The tubular portion of themotor housing 41 extends upward from the radially outer end portion ofthe bottom portion. The tubular portion of the motor housing 41 coversthe rotor 11 and the stator 12 from radially outside.

The bearing holder 42 has a bottomed tubular shape. That is, the bearingholder 42 has a bottom portion that expands in the radial direction. Thebottom portion of the bearing holder 42 has a through-hole penetratingthe axial central portion in the axial direction. The bus bar unit 13and the control board 21 are disposed radially inside the bearing holder42.

The bearing holder 42 has an upper bearing holding portion 421 at thecentral portion in the radial direction. For example, a lower tubularportion that is a cylindrical portion centered on the central axis CA isprovided at the bottom of the bearing holder 42. The lower tubularportion extends downward from the bottom portion of the bearing holder42. The upper bearing holding portion 421 is formed of a lower tubularportion. The upper bearing holding portion 421 holds the upper bearing102. More specifically, the upper bearing 102 is disposed inside thelower tubular portion constituting the upper bearing holding portion421.

The bearing holder 42 further includes a magnet accommodation portion422 at the center in the radial direction. For example, an upper tubularportion that is a cylindrical portion centered on the central axis CA isprovided at the bottom of the bearing holder 42. The upper tubularportion extends upward from the bottom portion of the bearing holder 42.The magnet accommodation portion 422 is configured by an upper tubularportion. The sensor magnet 110 is disposed inside the magnetaccommodation portion 422.

The bearing holder 42 has a through-hole 423 penetrating the bottomportion in the axial direction. The conductive wire of the coil 123extends through the through-hole 423. The conductive wire of the coil123 is drawn out from the lower side to the upper side of the bottomportion of the bearing holder 42 and is connected to the bus bar unit13.

The bearing holder 42 has a tubular portion. The tubular portion of thebearing holder 42 extends upward from the radially outer end portion ofthe bottom portion. The tubular portion of the bearing holder 42 coversthe bus bar unit 13 and the control board 21 from radially outside. Thetubular portions of the motor housing 41 and the bearing holder 42 arecoupled in the axial direction.

The motor cover 3 is between the bus bar unit 13 and the control board21 in the axial direction. That is, the motor cover 3 is disposedradially inside the bearing holder 42.

The upper cover 43 covers the upper opening of the bearing holder 42from above. That is, the upper cover 43 is fixed to the upper endportion of the tubular portion constituting the bearing holder 42. Forexample, the controller 2 includes a connector pin (not illustrated).The connector pin penetrates the upper cover 43 in the axial directionand protrudes to the upper side of the upper cover 43. The tubularportion 44 extending upward in a tubular shape is provided on the uppersurface of the upper cover 43. The tubular portion 44 surrounds theconnector pin protruding upward from the upper cover 43.

The upper cover 43 has an attachment portion 430 protruding downwardfrom the lower surface. The attachment portion 430 is a screw boss. Thatis, the attachment portion 430 includes a female screw portion (notillustrated) extending in the axial direction. The number of attachmentportions 430 is plural. The attachment portion 430 may be the samemember as the upper cover 43 or may be retrofitted to the upper cover43.

In addition, the controller 2 includes a screw 5. The screw 5 is usedfor fixing the control board 21. The control board 21 is attached to theattachment portion 430 using the screw 5. More specifically, the controlboard 21 has an attachment hole 210 (see FIGS. 9 and 10 ) penetrating inthe axial direction. The screw 5 is inserted into the attachment hole210 of the control board 21 from below and is screwed into the femalescrew portion of the attachment portion 430. As a result, a head portion51 of the screw 5 protrudes downward from the lower surface of thecontrol board 21. A plurality of screws 5 are used to attach the controlboard 21. For example, the number of screws 5 used is four. That is, thenumber of attachment portions 430 installed is four.

In this case, the motor cover 3 is disposed below the control board 21.Accordingly, when the control board 21 is attached, the head portion 51of the screw 5 faces the motor cover 3. That is, the screw 5 has thehead portion 51 located on the upper side (one side in the axialdirection) of the motor cover 3. In addition, the screw 5 has a screwportion 52 (see FIGS. 9 and 10 ) extending upward (one side in the axialdirection) from the head portion 51. The screw portion 52 is a malescrew.

FIG. 5 is a perspective view of the motor cover 3 according to theexample embodiment as viewed from above. FIG. 6 is a perspective view ofthe motor cover 3 according to the example embodiment with the reversesurface facing upward. FIG. 7 is a plan view of the motor cover 3according to the example embodiment as viewed from above. Referring toFIG. 7 , portions overlapping the screws 5 in the axial direction areindicated by the broken lines to clarify the positional relationshipbetween the motor cover 3 and the screws 5. FIG. 8 is a viewschematically illustrating a protruding portion 32 of the motor cover 3and its periphery according to the example embodiment. FIG. 9 is aschematic view illustrating the axial positional relationship betweenthe screw 5 inserted into the control board 21 and the motor cover 3.FIG. 10 is a view illustrating a state in which the screw 5 illustratedin FIG. 9 has moved downward. Referring to FIGS. 9 and 10 , theleft-right direction in each drawing is the radial direction, the leftside in each drawing corresponds to the radially outside, and the rightside in each drawing corresponds to the radially inside.

The motor cover 3 is a plate-like member. The motor cover 3 includes amain body portion 31. The main body portion 31 is formed in a circularshape centered on the central axis CA. The motor cover 3 has a holeportion 30 penetrating in the axial direction. The number of holeportions 30 is the same as the number of pins 130 of the bus bar unit13. The arrangement position of the hole portion 30 overlaps the pin 130in the axial direction. The pin 130 is inserted into the hole portion30. That is, the motor cover 3 has the hole portion 30 into which thepin 130 is inserted.

The motor cover 3 is welded to the bus bar holder 131 in a state inwhich the pin 130 is inserted into the hole portion 30. However, thepresent invention is not limited to this. For example, the pin 130 maybe a male screw. A male screw as the pin 130 may be inserted into thehole portion 30 from the upper side of the motor cover 3 and screwedinto the bus bar holder 131. For example, the motor cover 3 may be fixedto the bus bar holder 131 by providing a hook at the distal end of thepin 130 and inserting the pin 130 into the hole portion 30. That is, themotor cover 3 may be fixed to the bus bar holder 131 by a snap-fitmethod.

In this case, the motor cover 3 faces the head portion 51 of the screw 5in the axial direction. For example, of the four screws 5, the headportions 51 of the two screws 5 face the motor cover 3 in the axialdirection. An axial length L1 (see FIG. 9 ) of the screw 5 is longerthan a distance L2 (see FIG. 9 ) between the control board 21 and themotor cover 3 in the axial direction. That is, the axial length of thescrew 5 is longer than the distance between the controller 2 and themotor cover 3 in the axial direction. The axial length of the screw 5 isthe length from the lower end (the end on the other side in the axialdirection) of the head portion 51 to the upper end (the end on one sidein the axial direction) of the screw portion 52 of the screw 5.

The screw 5 is disposed at a position shifted from the hole portion 30of the motor cover 3 when viewed from the axial direction. Accordingly,when the screw 5 is loosened and moves downward, the head portion 51 ofthe screw 5 can be brought into contact with the motor cover 3. FIG. 10illustrates a state in which the screw 5 has moved downward. At thistime, since the axial length of the screw 5 is longer than the distancebetween the control board 21 and the motor cover 3 in the axialdirection, the screw 5 does not fall off, and the threadable engagementof the screw 5 with the attachment portion 430 can be suppressed frombeing completely released.

As a result, it is possible to suppress the generation of vibration inthe control board 21.

For example, the screw 5 protrudes radially outward from the main bodyportion 31 of the motor cover 3 when viewed from the axial direction.When viewed from the axial direction, the entire portion of the screw 5may be disposed radially outside the main body portion 31 of the motorcover 3.

Accordingly, the motor cover 3 has the protruding portion 32 thatprotrudes radially outward from the main body portion 31. The protrudingportion 32 faces the head portion 51 of the screw 5 in the axialdirection. Accordingly, when the screw 5 is loosened and moves downward,the head portion 51 of the screw 5 can be reliably brought into contactwith the motor cover 3.

Further, the width of the protruding portion 32 in the circumferentialdirection is larger than the diameter of the head portion 51 of thescrew 5. In other words, the protruding portion 32 has a first portion321 overlapping the head portion 51 of the screw 5 and a second portion322 extending from the first portion 321 to both sides in thecircumferential direction when viewed from the axial direction.Referring to FIG. 9 , the first portion 321 is hatched to bediscriminated from the second portion 322. Referring to FIG. 8 , theleft-right direction in the drawing corresponds to the circumferentialdirection.

Since the protruding portion 32 has the second portion 322, when thescrew 5 is loosened and moves downward, the head portion 51 of the screw5 can be brought into contact with the motor cover 3 even if thepositional relationship between the motor cover 3 and the screw 5 ischanged by an assembly error or the like. For example, even if theposition of the screw 5 when viewed from the axial direction is shiftedin the circumferential direction with respect to the first portion 321,the head portion 51 of the screw 5 can be brought into contact with thesecond portion 322.

The motor cover 3 has a rib 33. The rib 33 protrudes in the axialdirection and extends in the radial direction. More specifically, theplurality of ribs 33 radially extend from the central portion in theradial direction. Each of the plurality of ribs 33 extends linearly inthe radial direction.

The protruding portion 32 is disposed ahead in the direction in whichone of the ribs 33 extends. That is, the protruding portion 32 is on aline extending in the same direction as the rib 33 when viewed from theaxial direction. This can suppress the vibration of the motor cover 3.The rib 33 may be formed to extend to the protruding portion 32.Referring to FIG. 7 , a line extending in the same direction as the rib33 is indicated by the two-dot chain line, and a reference sign L isgiven.

In addition, the motor cover 3 includes, as the ribs 33, obverse surfaceribs 331 protruding upward (to one side in the axial direction) from theupper surface and reverse surface ribs 332 protruding downward (to theother side in the axial direction) from the reverse surface opposite tothe obverse surface. As a result, the vibration of the motor cover 3 canbe further suppressed as compared with the case in which the rib 33 isformed only on one surface of the motor cover 3.

For example, the motor cover 3 further includes annular ribs 34. Theannular ribs 34 are provided on both surfaces, namely, the obversesurface and the reverse surface. The annular rib 34 has an annular shapecentered on the central axis CA when viewed from the axial direction.The ribs 33 extend radially outward from the annular ribs 34 as viewedin the axial direction. Note that the number of annular ribs 34 on thesurface is one (see FIG. 5 ). On the other hand, a plurality of annularribs 34 are formed on the reverse surface (see FIG. 6 ).

The motor cover 3 is made of a resin. For example, the motor cover 3 isa resin molded product. Accordingly, the motor cover 3 having theprotruding portion 32 can be easily formed. In addition, the ribs 33 canbe easily provided on the obverse and reverse surfaces of the motorcover 3.

The motor cover 3 has a mark 35 for suppressing the occurrence of workmistakes in the attaching process with respect to the bus bar unit 13.The mark 35 is a notch cut radially inward from the outer edge of themotor cover 3. Providing the mark 35 on the motor cover 3 can preventthe motor cover 3 from being attached at a circumferential positionshifted from the correct position in the attaching process for the motorcover 3.

The example embodiment of the present invention is described as above.Note that the scope of the present invention is not limited to theabove-described example embodiment. The present invention can beimplemented with various modifications within a scope not departing fromthe gist of the invention. Further, the above-described exampleembodiment can be appropriately and optionally combined.

The present invention can be applied to, for example, an electric powersteering device used for assisting steering wheel operation of a vehiclesuch as an automobile.

Features of the above-described example embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While example embodiments of the present disclosure have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present disclosure. The scope of the presentdisclosure, therefore, is to be determined solely by the followingclaims.

What is claimed is:
 1. A motor assembly comprising: a motor including arotor rotatable about a central axis and a stator radially opposing therotor; a controller on one side in an axial direction of the motor tocontrol the motor; and a motor cover between the motor and thecontroller in the axial direction and covering the motor from the oneside in the axial direction; wherein the controller includes a screw;the screw includes: a head portion located on the one side in the axialdirection of the motor cover; and a screw portion extending from thehead portion to the one side in the axial direction; the motor coveropposes the head portion in the axial direction; a length of the screwin the axial direction is longer than a distance between the controllerand the motor cover in the axial direction; the motor includes a pinextending to the one side in the axial direction; the motor coverincludes a hole portion into which the pin is inserted; and the screw isat a position shifted from the hole portion as viewed in the axialdirection.
 2. The motor assembly according to claim 1, wherein the motorcover includes: a main body portion, and a protruding portion thatprotrudes radially outward from the main body portion; and theprotruding portion axially opposes the head portion.
 3. The motorassembly according to claim 2, wherein a circumferential width of theprotruding portion is larger than a diameter of the head portion asviewed in the axial direction.
 4. The motor assembly according to claim2, wherein the motor cover includes a rib protruding in the axialdirection and extending in a radial direction; and the protrudingportion is on a line extending in the same direction as the rib whenviewed from the axial direction.
 5. The motor assembly according toclaim 4, wherein the rib of the motor cover includes an obverse surfacerib protruding from an obverse surface on the one side in the axialdirection to the one side in the axial direction and a reverse surfacerib protruding from a reverse surface opposite to the obverse surface tothe other side in the axial direction.
 6. The motor assembly accordingto claim 1, wherein the motor cover is made of a resin.